Large study finds no meaningful link between meat consumption and depression

A new study published in the journal Psychological Science suggests that the link between eating meat and experiencing depression is extremely weak and likely not causal. By analyzing data from tens of thousands of people over several years, scientists found that avoiding meat does not appear to be a meaningful risk factor for developing depression. This provides evidence that people choosing vegetarian or vegan diets do not need to worry about their dietary choices directly causing a decline in their mental health.

In recent years, public interest in the potential mental health impacts of plant-based diets has grown. “Some studies have suggested a link between avoiding animal products and depression, and some social media influencers have recommended eating meat to avoid depression,” said researcher Christopher Hopwood. “Previous studies have not been able to estimate a population-level effect or examine the preconditions of causality as we did in this study.”

Many earlier projects asked people to identify themselves as vegetarians, vegans, or omnivores. This categorizing approach can be flawed because a person’s chosen dietary label does not always match their actual eating behavior. To address this, the current study treated meat consumption as a continuous behavior, measuring exactly how often a person eats animal products.

Past projects also often relied on small, non-representative groups of people, making it difficult to apply the findings to the broader population. Scientists noticed that previous work frequently ignored other life factors that influence mental health, such as age, income, education, and gender. The researchers designed this project to see if the supposed link between meat consumption and depression was actually caused by these outside demographic variables.

To gain a more accurate understanding, the scientists analyzed existing data from three massive, ongoing national surveys. These included panels from the Netherlands, Germany, and Australia. In total, the study included a highly representative sample of 77,678 participants.

The participants regularly completed questionnaires detailing how often they ate meat, fish, and poultry. The frequency options ranged from never eating meat to consuming it daily or even multiple times a day. Participants also answered standardized questions about their mental well-being, specifically indicating how often they felt sad, hopeless, or lacking in energy over the previous four weeks.

By using these repeated measurements, the scientists could track changes in both diet and mood for each specific person over time. In their statistical analysis, the researchers controlled for age, gender, income, and educational background. This adjustment helps isolate the specific relationship between diet and mood by removing the influence of demographic factors that are known to affect both.

The scientists found a very weak negative correlation between meat consumption and depression. The statistical association was so small that it is unlikely to have any noticeable impact on a person’s everyday life. “The general pattern is that eating meat has basically no impact one way or the other on depression,” Hopwood said.

When looking at the longitudinal data, the researchers tested for what is known as a lagged effect. They wanted to see if a person eating less meat than their own personal average at one point in time predicted higher depression scores at the next survey assessment. They found no significant delayed effects, meaning a reduction in meat intake did not predict an increase in depressive symptoms in following years.

The researchers also checked if experiencing depression caused people to change their diets later on. They found no evidence for this reverse effect either. Additionally, they tested whether living in a rural versus an urban setting changed the relationship between meat consumption and depression, but they found no contextual differences.

The scientists also looked for non-linear patterns, checking if both extremes of meat-eating might be linked to poor mood. “There was a spike in depression at very high levels of meat consumption, suggesting that eating too much meat might be related to depression,” noted Hopwood. Even so, the data overall indicated that people who eat average amounts of meat report the lowest levels of depression.

While these findings are detailed, the study relied exclusively on self-reported data, which means participants had to accurately remember and report their own eating habits and feelings. “We could not test causality directly, but the results strongly suggest that a causal link is unlikely,” Hopwood said. “Also, we only tested people in three Western countries, and it is possible that results would differ in other cultures.”

Age and life circumstances might also play an unmeasured role in mental health and diet. “There are certain developmental or life stages when nutrition needs change (e.g., during pregnancy, following exposure to animal agriculture) and these results did not examine those issues closely,” Hopwood explained. Future research could benefit from using more frequent assessments to track rapid shifts in mood and eating behavior.

Moving forward, the researchers hope to examine how diet affects specific mental health conditions. “We think the findings from this study are definitive regarding meat consumption and depression in the general population, but there may be certain sub-groups for whom there is a link, such as people with eating disorder diagnoses or people with significant anxiety about the environment or animal rights,” Hopwood said. “We would be interested in studying those sub-groups.”

The researchers want to provide reliable information for public health and wellness. “We think it is important for people to make dietary decisions based on evidence and are concerned about people making decisions that could harm themselves, the environment, or animals based on uninformed opinions shared on social media,” Hopwood added. “We hope that these results offer such people evidence with which to make good dietary decisions.”

The study, “Associations between meat consumption and depression are small and unlikely to be causal,” was authored by Nicholas Poh-Jie Tan, Michael D. Krämer, Peter Haehner, Wiebke Bleidorn, and Christopher J. Hopwood.